Condensed Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:
Property rental	$ 113,881	$ 94,065	$ 324,144	$ 249,193
Tenant reinsurance	12,294	9,495	34,625	27,060
Management fees	6,936	6,231	19,910	19,476
Total revenues	133,111	109,791	378,679	295,729
Expenses:
Property operations	34,376	30,115	102,275	82,723
Tenant reinsurance	2,873	1,379	6,985	4,651
Acquisition related costs	2,427	2,486	3,562	3,564
General and administrative	13,943	12,559	40,451	37,744
Depreciation and amortization	23,428	19,768	69,238	52,918
Total expenses	77,047	66,307	222,511	181,600
Income from operations	56,064	43,484	156,168	114,129
Gain on sale of real estate assets			800
Loss on extinguishment of debt related to portfolio acquisition	(9,153)		(9,153)
Interest expense	(16,264)	(18,423)	(51,992)	(52,348)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(834)		(947)	(444)
Interest income	202	461	519	1,184
Interest income on note receivable from Preferred Operating Partnership unit holder	1,213	1,213	3,638	3,638
Income before equity in earnings of unconsolidated real estate ventures and income tax expense	31,228	26,735	99,033	66,159
Equity in earnings of unconsolidated real estate ventures	3,405	2,854	8,942	7,848
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of joint venture partners' interests		13,620	2,556	19,049
Income tax expense	(2,281)	(1,656)	(7,147)	(4,240)
Net income	32,352	41,553	103,384	88,816
Net income allocated to Preferred Operating Partnership noncontrolling interests	(2,033)	(1,805)	(5,495)	(5,108)
Net income allocated to Operating Partnership and other noncontrolling interests	(1,074)	(1,142)	(2,753)	(2,475)
Net income attributable to common stockholders	$ 29,245	$ 38,606	$ 95,136	$ 81,233
Net income per common share
Basic (in dollars per share)	$ 0.26	$ 0.37	$ 0.86	$ 0.81
Diluted (in dollars per share)	$ 0.26	$ 0.37	$ 0.84	$ 0.80
Weighted average number of shares
Basic (in shares)	111,231,452	104,252,227	111,060,997	100,429,840
Diluted (in shares)	117,604,515	108,755,316	117,483,010	104,981,176
Cash dividends paid per common share (in dollars per share)	$ 0.40	$ 0.20	$ 1.05	$ 0.60